Chizuko Ogata

An Active Intraoral Shape Measurement Scheme Using a Compact Compound-Eye Camera with Integrated Pattern Projectors

We propose an active intraoral shape measurement scheme to realize a compact intraoral diagnostic system for measuring the three-dimensional shapes of gums and teeth. To measure intraoral surfaces with little texture, compact pattern projectors based on diffractive optical elements are integrated in lens gaps of a compact compound-eye camera called a thin observation module by bound optics (TOMBO). The three-dimensional shape is reproduced on the basis of triangulation using the amount of pattern distortion. A scaled-up prototype system is constructed to verify the measurement scheme using the TOMBO camera and a spatial light modulator. The prototype system demonstrates an rms distance accuracy of 0.46 mm. A temporal change of the shape is quantitatively evaluated with a reference surface based on teeth positions.

A compact shape-measurement module based on a thin compound-eye camera with multiwavelength diffractive pattern projection for intraoral diagnosis

We have proposed a compact three-dimensional shape-measurement system for intraoral diagnosis, in which multiwavelength pattern projectors based on diffractive optical elements (DOEs) are integrated in the lens gaps of a compound-eye camera. We have built a prototype module with blue and green pattern projectors in both sides of the compound-eye camera to increase in-plane spatial resolution. With the two projectors, the stripe pitch was reduced to 0.73 mm in average from about 1.4 mm for one wavelength. Root-mean-square (rms) error of the measured depth map of a plane board was 0.27 mm at the distance of 40 mm. The rms errors for the measured results of the gums and teeth of a plaster figure and an examinee were 0.37 and 0.40 mm, respectively.

A stick-shaped multi-aperture camera for intra-oral diagnosis

A stick-shaped TOMBO (thin observation module by bound optics) was developed for intra-oral diagnosis. The module consists of 3×3 imaging units which are designed to capture different optical signals. Embedded functions were stereo 3D monitoring, depth estimation, and tissue assessment. Illumination equipments and a pattern projector were integrated in the module. Teeth and gingiva of several subjects were observed. 3D shape of gingiva was retrieved from a couple of unit images. The boundary between the attached gingiva and the alveolar mucosa as well as the spatial distribution of melanin were estimated using multiple linear regression analysis. The observed signals were confirmed to be useful for odontotherapy.